I had Francis, my #4 cat, chipped because he has shown an inclination to
try to get out the door when it's opened, but cats 1-3 show no such
desire, so I haven't had them chipped.  The chip's so tiny I have yet to
find it with my fingers between Francis' shoulder blades.

Priscilla

On Sun 13 Mar 2005 05:58:45p,  wrote in rec.pets.cats.health+behav
(news:1110754725.256582.175290@f14g2000cwb.googlegroups.com):

I'm thinking about having all of mine chipped. They don't go out, and
have no inclination to do so, but there are too many other ways that
they might get loose. One of mine got out when a worker in my house
didn't shut the door tight, but he noticed him outside and alerted me
to it. I was never so scared in my life. Shamrock was disoriented
being outside, scared, and ran straight toward the busy road. Luckily
he turned quickly and ran into my fenced backyard.

Suddenly, without warning, Telecomdani@aol.com exclaimed (3/13/2005
10:58 PM):

Meep was chipped back in 2001.  She didn't even notice that it'd been
done, it's been readable in 3 different countries, and has caused her
absolutely no problems.  I can sometimes feel it if I give her a deep
shoulder massage, but that's been getting rarer.

Here in the UK, there's a national registry, but the name escapes me.  I
think there are multiple registries in the US.  Having the chip #
registered means that if Meep ends up in a shelter, she has an
infinitely better chance of finding her way home, assuming the shelter
has a chip reader.  Just in case, I also have her chip number in a slip
of paper in a little barrel tag on her collar.

I do have a vet wave a wand over her every year or so, just to make sure
the chip is still active.

Even if your cat is completely indoors (and perhaps because), chipping
should be considered - no telling how your cat may react if suddenly
outside of their house - either as an escapee, or as the result of (god
forgive) a break-in, or fire, or any number of other ways of getting
lost (accident on the way to the vet also comes to mind).